Automatically expanding the zoom capability of a wide-angle video camera

ABSTRACT

A system for automatically expanding the zoom capability of a wide-angle video camera using images from multiple camera locations. One preferred embodiment achieves this using images from the wide-angle video camera that are analyzed to identify regions of interest (RoI). Pan-Tilt-Zoom (PTZ) controls are then sent to aim slave cameras toward the RoI. Processing circuitry is then used to replace the RoI from the wide-angle images with the higher-resolution images from one of the slave cameras. In addition, motion-detecting software can be utilized to automatically detect, track, and/or zoom in on moving objects.

CROSS-REFERENCE TO OTHER APPLICATIONS

This application claims priority from provisional U.S. patentapplication 60/589,104 filed Jul. 19, 2004, which is hereby incorporatedby reference.

BACKGROUND AND SUMMARY OF THE INVENTION

1. Field of the Invention

The present inventions relate to video monitoring systems, and morespecifically, to automatically expanding the zoom capability of awide-angle video camera.

2. Background

Real-time video surveillance systems have become increasingly popular insecurity monitoring applications. A new class of cameras replaces themechanical Pan-Tilt-Zoom (PTZ) functions with a wide-angle opticalsystem and image processing, as discussed in U.S. patent applicationSer. No. 10/837,019 entitled “Method of Simultaneously DisplayingMultiple Views for Video Surveillance,” which is hereby incorporated byreference. This class of cameras is further discussed in U.S. patentapplication Ser. No. 10/837,325 entitled “Multiple View Processing inWide-Angle Video Camera,” which is hereby incorporated by reference.This type of camera monitors a wide field of view and selects regionsfrom it to transmit to a base station; in this way it emulates thebehavior of a mechanical PTZ camera. The wide-angle optics introducesdistortion into the captured image, and processing algorithms are usedto correct the distortion and convert it to a view that has the sameperspective as a mechanical PTZ camera.

The U.S. patent application Ser. No. 10/837,326 entitled, “MultipleObject Processing in Wide-Angle Video Camera” by Yavuz Ahiska, which ishereby incorporated by reference, describes a way to correct thedistorted view captured by a wide-angle camera. This camera, even usingthis distortion-correction process, only has limited capabilities tozoom into a region of interest. The camera can also be a programmableone as described in U.S. patent application Ser. No. 10/837,325,entitled “Multiple View Processing in Wide-Angle Video Camera,”containing programmable embedded microprocessors.

There exists a conflict between a video camera's field of view and theeffective resolution of its image. Wide-angle lenses rarely offer anysignificant optical zoom, and similarly, video cameras with a high zoomcapability have restricted fields of view (especially when theirmagnification is increased).

A solution to monitoring a wide-angle area while being able to captureregions at a higher detail is to utilize multiple cameras at differinglocations. The U.S. Pat. No. 6,724,421, which is hereby incorporated byreference, and the public domain document, “A Master-Slave System toAcquire Biometric Imagery of Humans at Distance,” by X. Zhou et al,which is hereby incorporated by reference, describe systems usingmultiple cameras to monitor a wide-angle area. In these systems, aseparate base station unit controls the two cameras monitoring thescene. In addition, these systems do not try to expand the zoom functionof the master camera.

The U.S. Pat. No. 6,147,709, which is hereby incorporated by reference,describes a method and apparatus for overlaying a high-resolution imageonto a hemispherical interactive image captured by a camera by matchingat least three points between the high-resolution image and theperspective corrected image. A major drawback with this process is thatit makes comparisons in the perspective corrected domain.

Moving regions in a video corresponding to persons or moving objects,together with tracked objects which may no longer be moving, and theirlocal neighborhoods in the video define Regions of Interest (RoI)because persons, moving and/or tracked objects, etc. are important insecurity monitoring applications. In order to provide real-time alarmsfor dangerous events, RoI should be tracked and zoomed for closerinspection. Conventional Closed Circuit Television (CCTV) systems, whichonly capture recorded video for later analysis, cannot provide automaticalarm and event triggers without delay.

A wide field of view camera that can both monitor a wide-angle scene,while also being able to simultaneously and automatically captureregions of interest at a greater magnification is very desirable insurveillance systems. For example, a high-resolution image could makethe difference in positively identifying a criminal committing anoffense or the detail surrounding an unattended suitcase. Therefore, itis very important to provide a high-resolution view of a person in asurveillance application.

Wide-angle surveillance is necessary in many CCTV applications. Camerassuch as dome cameras and cameras with fisheye or peripheral lenses canproduce wide-angle video. A major weakness of wide-angle surveillancecameras and systems is that they either do not have the capability tozoom into a RoI or are limited in their zooming capability.

The system can also have a computer program comprising amachine-readable medium having computer executable program instructionsthereon for executing the moving object detection and object trackingalgorithms fully in the programmable camera device as described in U.S.patent application Ser. No. 10/924,279, entitled “Tracking MovingObjects in Video Using Wavelet Domain Information,” by A. E. Cetin andY. Ahiska, which is hereby incorporated by reference. Automaticmoving-object detection and object tracking capability of the wide fieldof view camera can define a RoI in the wide-angle scene monitored by thecamera containing the object in question. As this RoI will be ofinterest in many security applications, the region can be tracked by theelectronic PTZ capability of the master camera.

There is a present demand for a system that can both monitor a widearea, while also being able to simultaneously and automatically captureregions of interest at a higher resolution.

Automatically Expanding the Zoom Capability of a Wide-Angle Video Camera

The present innovations include a new approach that achieves the abilityto monitor a wide-angle area while being able to capture regions ofhigher detail.

In one example embodiment, a wide-angle, master camera, such as a domecamera or a camera with a fish-eye or peripheral lens, preferably withsubstantially no zoom capabilities, is used to capture images andautomatically identify RoI, e.g. motion detecting and/or objecttracking. In this embodiment, at least one other camera, preferably withexpanded zoom capabilities relative to the master camera, can be used tozoom into the identified RoI. The views from the cameras other than themaster camera can be used for several purposes including, but notlimited to, input into the master camera or output to a base station.

In another example embodiment, control circuitry sends PTZ controls toone or more slave cameras based in at least partial dependence on thewide-angle images captured by the master camera. Among other things,these controls can be used to aim the slave camera towards the RoIand/or zoom the slave camera onto the RoI.

In another class of embodiments, the output of a slave camera iscompared to the images captured by the master camera and PTZ controlsare sent to one or more slave cameras based in at least partialdependence on the comparison. Output images from the slave cameras canthen be used for several purposes including, but not limited to,comparing them to RoI from the master camera, outputting them to a basestation, or overlaying them onto other images.

In a sample of this embodiment, after the slave camera has moved inaccordance with the PTZ controls, the output from the slave camera canbe compared to the images from the master camera to generate a new setof PTZ controls. This process can be, but does not have to be, used tomatch the output images from the slave camera to the RoI identified inthe output images from the master camera. This process can be, but doesnot have to be, an iterative process that can be repeated to yield anylevel of desired matching accuracy. There are multiple methods forimplementing this synchronization including, but not limited toimage-processing techniques to match views, calibration procedures, orposition analysis of feedback from the slave camera.

In another example embodiment, the images from the slave camera can beused to replace, correct, inset, or overlay some or all of the imagesfrom the master camera. The composite images can be used for severalpurposes including, but not limited to, recording them, outputting themto a base station, and/or using them to generate PTZ controls.

In another embodiment, several slave cameras, preferable monitoringdifferent regions, can be used and the perspective-corrected view of themaster camera can be altered in at least partial dependence on theadjusted views of at least one of these slave cameras.

In another embodiment, motion-detecting software can be utilized todefine the RoI as moving regions in the video corresponding to, but notlimited to, persons, moving objects, tracked objects which may no longerbe moving, and/or their local neighborhoods in the video.

These and other embodiments of the present innovations are describedmore fully below.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed inventions will be described with reference to theaccompanying drawings, which show important sample embodiments of theinvention and which are incorporated in the specification hereof byreference, wherein:

FIG. 1A shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 1B shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 2 shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 3 shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 4 shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 5 shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 6 shows a diagram of a camera system consistent with a preferredembodiment of the present invention.

FIG. 7 shows a flowchart implementing process steps consistent with thepreferred embodiment of the present invention.

FIG. 8 shows a flowchart implementing process steps consistent with thepreferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment (by way of example, and not of limitation).

Before the present innovations, the systems available only had limitedzoom capabilities, but using a slave PTZ camera controlled from themaster camera can expand this electronic-zooming capability to get evenhigher resolution images of the RoI.

Unlike U.S. Pat. No. 6,147,709, the method and systems disclosed belowwhich make comparisons do so in the wide-angle distorted domain withinthe master camera, as opposed to the perspective corrected domain, togenerate PTZ commands for controlling a slave PTZ video camera. This canbe an iterative process, and yields the desired matching accuracy givenenough steps.

The control system within the master camera that performs view matchingbetween a master, wide-angle video camera and a slave PTZ camera allowsthe master camera to acquire detailed images of required areas from theslave camera. There are multiple methods for implementing thissynchronization namely using image-processing techniques to match viewsand/or by a calibration procedure. Position feedback from the slavecamera can also be a useful element of information for accurate viewmatching. The U.S. Pat. No. 6,509,926 entitled “Surveillance Apparatusfor Camera Surveillance System,” which is hereby incorporated byreference, discusses a system for generating the azimuth and elevationangles of a camera and lens. Carrying out this process in the distorteddomain allows the comparison to be made without losing anything in termsof quality. Comparing images or vectors x and y can be measured manydifferent ways, the most well known way is the Euclidian distance,∥x−y∥, but can also use ∥g(x)−g(y)∥ where g is an appropriate functionrepresenting the distortion.

In a preferred embodiment, the master wide-angle camera has thecapability of sending PTZ control signals to the slave PTZ camera tozoom into the RoI in an automatic manner by implementing themotion-detection and/or object tracking algorithms on the current widefield of view image. In an example embodiment, the slave is commanded togo to a set angle, which can be described as a PTZ control although itis not the standard widespread PTZ interface. A control system residentin the master camera can perform view matching between the master,wide-angle video camera and the slave PTZ camera. One preferredembodiment uses image-processing techniques to match the views of themaster and slave cameras, allowing detailed images of the RoI to beacquired.

In one class of embodiments, the master and slave cameras are calibratedand PTZ controls can be sent to the slave camera based at leastpartially on these calibrations. If calibration between the master andslave cameras is insufficient alone, image registration or matching canbe carried out either using the corrected images of the scene or usingthe raw wide-angle images captured by the master camera.

The following is one possible example of the calibration process betweenthe master and slave cameras. It provides a switching mode where themaster camera's output can be switched to the slave camera's output, theswitch can be based on a predefined zoom point where the slave camera'sposition can then be lined up with the master camera's selected viewand, if slave tracking is being used, the slave camera can be used tofollow an object being tracked by motion tracking. The master camera'swide-angle view can be divided into smaller regions and, using imageprocessing, these regions can be zoomed in on. By tracking these smallerviews, the master camera is acting as a virtual camera, or VCAM. Asmentioned earlier, the zoomed in VCAM views have smoothed edges andblurred details. The slave camera views are needed to capture the levelof detail required in most surveillance applications.

Manual Mode:

The video of Head A (in one preferred embodiment this refers to view ofthe output from the master camera) is switched to the video output ofthe slave camera on pressing the enter key. Once switched, keyboardcontrol of the slave camera is provided. The slave camera can then bemanually calibrated to aim at the same object as the master camera.Pressing escape returns the video and keyboard control to the mastercamera. In another example embodiment, there can be two analogue outputsfrom the master camera, each referred to as a Head. A monitor can viewthe output from a Head. There can be BNC connectors at the back of themaster camera, labeled A and B so that a monitor can be connected toeither Head A or Head B.

Zoom Switch Mode:

While controlling any VCAM on Head A, if the field of view goes beyond25 degrees, the video is switched to the slave camera and it is moved tothe same position as the master camera's VCAM. An option is provided forpre-positioning. If this option is turned on, the slave camera will bemoved to the position of the master camera's VCAM at a zoom level of 30degrees and is repositioned until the zoom level reaches 25 degrees atwhich point the video is switched to the slave camera. Once switched,keyboard control of the slave camera is provided. Pressing escapereturns the video and keyboard control to the master camera.

Slave Tracking Mode:

Whenever motion tracking is triggered, Head A is switched to the slavecamera and the slave camera is moved to the position of the motionrectangle being tracked and is updated as the motion rectangle moves. Ifthe motion rectangle stops moving or slows down the slave camera iszoomed in and will zoom out again if the motion rectangle moves fasteragain. If the user moves the joystick, control of the slave camera willbe given to them. If after 5 seconds of no activity from the keyboardthe camera is still tracking, it will return the slave camera totracking the motion rectangle. If tracking has ended control and videowill be returned to the master camera.

Design

Three additional classes were required in order to implement themaster/slave features; slavecalibration, slavemanager and serialout. Thecode described here is enabled via the abspos setting within theadome.ini.

Slavecalibration:

This class is responsible for calibrating the master camera with theslave camera and translating between the master camera sphericalcoordinates and slave camera spherical coordinates.

The calibration phase is run by positioning the slave camera at areference point.

Its video output is then displayed on Head A while a VCAM is positionedat the same reference point. (but in the coordinate system of the mastercamera). The user then has control of positioning of the master camera'sVCAM and should line up the VCAM to match the image from the slavecamera. Once matched, the user would press enter and the currentposition of the VCAM would be read. The difference in pan between thereference point and the new position of the VCAM is stored for later useby the translation function. For the calibration phase theslavecalibration class collaborates with the Menus class and it ispossible to use more than one reference point if required withoutchanging the Menus class (see GenerateCalibrationPresets function of theslavecalibration class).

The second responsibility of the slavecalibration class is to provide atranslation of the master camera's coordinates to the slave camera'scoordinates for the slavemanager class. This is done in theTranslateToSlaveCoordinates function by firstly assuming that the pointbeing viewed is a distance of 5 meters away. The spherical coordinatesare then translated into Cartesian coordinates. A rotation in the z-axisby the difference in pan that was measured during the calibration phaseis then made. A translation in x and z coordinates is then made. Thistranslation is accounting for the physical distance between the twocameras (including their difference in height). The mounting kit willensure that the distance between the two cameras is constant along thex-axis. As the height of the slave cameras can be different from oneanother the z-axis translation depends on which slave camera isconnected. The final stage is to convert the translated and rotatedCartesian coordinates back into spherical coordinates.

Slavemanager:

The slavemanager class is responsible for checking the zoom level forwhen to switch to the slave camera, switching the video to the slavecamera, positioning the slave camera and dealing with timeouts from nokeyboard activity.

The ProcessSlaveMode function is called once per frame. If the zoomswitch is enabled it will check the zoom level of the active VCAM onHead A and if it is under 25 it will switch to the slave camera andposition it by calling the SetSlaveMode function (described below). Ifprepositioning is enabled it will also position the slave camera, butnot switch to it when the zoom level is between 30 and 25. This is doneby calling the SwitchSlaveToNearestPreset function (described below). Atimer is managed by the class in order to deal with timeouts from slavemode and slave tracking mode. This timer is checked in this function andthe appropriate mode entered after a timeout. The timer is reset bycalling the SlaveMoved function (this is done by serialOut and serialdescribed below).

The SetSlaveMode function switches the video to the slave camera andpositions it. The switch to the slave camera video is done by setting abit of the register controlling the CPLD via an i2c write. Thepositioning is carried out by reading the current position of the activeVCAM, translating the coordinates by calling theTranslateToSlaveCoordinates function of the slavecalibration class andpassing it to the output queue for the serialout class to deal with(described below).

The SwitchSlaveToNearestPreset function takes the master camera'sspherical coordinates, uses the TranslateToSlaveCoordinates function ofthe slavecalibration class and passing it to the output queue for theserialout class to deal with (described below). This is used by theprepositioning and by the MotionTracker class for slave tracking(described below).

Serialout:

The serialout class is responsible for sending commands to the slavecamera via RS485. The serialout class runs a separate thread, whichblocks on the output queue until a command is added to the queue. Once acommand is added to the queue it calls the appropriate send function onthe serial class.

In addition to the new classes described above some changes have beenmade to existing classes. The key changes are described below:

Serial:

The serial class that deals with keyboard input has the addition of apassthrough mode which is enabled when in slave mode, slave trackingmode or slave calibration mode. In the passthrough mode all commandsreceived are passed out of the second serial port (the one connected tothe slave dome). The escape key is captured by the serial class while inthis mode and slave mode is disabled when it is received (by calling theSetSlaveMode function of SlaveManager). While in this mode theSlaveMoved function of Slavemanager is called every time a command isreceived from the keyboard and passed through. This prevents theslavemanager from timing out of the mode by reseting its timer.

MotionTracker:

The MotionTracker class, that deals with motion tracking, has anadditional function, SetSlavePos, that is called when the motiontracking moves the tracking VCAM camera slave tracking is enabled.

The SetSlavePos function takes the raw motion rectangle and the zoomlevel decided upon by the motion detection and tracking algorithms usedfor the tracking VCAM. It then attempts to position the slave camera sothat it is centered on the top half of the motion rectangle (this is asimple aim high system attempting to aim for the persons head). If theposition decided upon for the slave is less than a defined thresholdaway from the current position of the slave camera, the slave camera isleft where it is. This is in order to reduce the number of small movesmade by the slave camera—when the slave camera is moved it stops quitesuddenly so a slight vibration effect can be noticed so the algorithmprefers larger movements rather than lots of small movements in order toreduce the impact of this effect.

If the motion rectangle is moving slowly or stops the algorithm willcause the slave camera to zoom in further than the zoom value calculatedby the VCAM's motion tracking algorithm. This is achieved by creating am_DistanceMoved variable. This variable is set to 100 when trackingbegins. During tracking the value is recalculated by taking 80% of itscurrent value and 20% of the distance the slave dome has been moved by(straight line distance) since the last time it was moved. When thisvalue drops below 3 the zoom level is increased before the slave camerais positioned. If the value is greater than or equal to 3 the zoom levelis set to the one calculated by the VCAM's motion tracking algorithm.The above embodiments are only example implementations and are notintended to limit the many possible ways that the present innovationscan be implemented.

In one example embodiment, the images are compared in the same domain,e.g., distorted or corrected domain. In order to compare images in thewide-angle image domain, the images of the slave camera go through areverse transformation into a distorted view similar to that of aportion of the raw wide-angle image of the master camera. The images canthen be compared and, in one example embodiment, controls can be sent inat least partial dependence on the results of this comparison. Themaster camera can adjust the PTZ control signals according to the imagematching results so that RoI is in the center of the field of view ofthe slave camera.

Image matching can be implemented in an iterative manner to increase theaccuracy of the view matching between the RoI and the field of view ofthe slave camera or cameras. This image matching can be done in manyways. Some of these methods are described in the public domain textbook,“Fundamentals of Digital Image Processing” by Anil Jain, Prentice-Hall,NJ, 1988. In an example of this embodiment, the master camera can sendincremental PTZ control signals in order to achieve any level of desiredmatching accuracy.

Once the two images are matched or registered, the perspective correctedview of the master camera can be replaced by the revised view from theslave camera to have a higher resolution image of the RoI than wouldhave been possible with the zooming capability of the master cameraalone. The slave PTZ camera, having optical zooming capability, producesa sharper image of the RoI compared to the corrected view of the RoIobtained from the master wide-angle camera. This is because somewide-angle cameras zoom into a region by performing numericalinterpolation, which may smooth the edges of the objects in the RoI. Inthis example embodiment, replacing an image from the master camera withthe sharper image obtained from the slave camera expands the zoomingcapability of the master camera.

Examples of preferred embodiments are shown in FIGS. 1 through 9. Anexample embodiment of the inventions is shown in FIGS. 3, 4, and 5containing programmable embedded microprocessors and circuitry. Apreferred embodiment can have the capability of performing all necessaryimage processing operations to achieve an expanded optical zoom.

FIG. 1A shows a preferred layout for the system including a preferredembodiment of the master wide-angle camera. The wide-angle opticalsystem, 101 in conjunction with the image sensor 102, captures an imagethat can be passed to the image processing circuitry 103 for correction.In one example embodiment, the correction can be an image warp thatcompensates for distortions introduced by the lens. As disclosed in U.S.patent application Ser. No. 10/837,012, entitled, “Correction of OpticalDistortion by Image Processing,” which is hereby incorporated byreference, the distortion may be arbitrarily complex. The distortion canbe corrected through the use of tables that define the necessarywarping. The image processing circuitry 103, which has a memory, can beimplemented in several ways, including either one or a cascaded set ofmicroprocessors coupled with a high bandwidth bus to increase theavailable processing capability. The digital sensor data can be sent tothe image processing circuitry 103 through a buffer or directly if thecircuitry operates at a sufficiently high speed. This circuitry can alsobe responsible for debayering, color equalization and color balancing ofthe image. Characteristics of the image sensing 102, such as theexposure and aperture, and the image processing 103 can be controlled bythe control circuitry 104. The output circuitry 105 can be used to output a video signal to the base station.

The image processing circuitry 103 in the master camera can also takethe digital video from the slave PTZ camera as another input. The viewfrom the slave camera can be used when an image with a greater opticalzoom is desired for improved detailed. The decision for whether the viewfrom the slave is necessary can be dictated by the control circuitryresident in the master camera 104, which acts on a resident softwareprogram and from base station control. The control from the base stationcan be any standard, including RS485 or TCP/IP format. The slave camerais not controlled directly from the base station, but via the controlcircuitry, preferably in the master camera 104.

In an example embodiment, the control circuitry 104 performs anyrequired view matching between the master, wide-angle video camera andthe slave PTZ camera. PTZ controls can be transmitted to the slavecamera from the control circuitry in the master camera to achieve aninitial approximate matching. This approximation can, for example, PTZpresets in the slave camera. There is an optional position feedbacksignal from the slave camera, which aids the control circuitry inpositioning the slave PTZ camera to the desired location.

In a preferred embodiment, this matching can be assisted usingimage-processing techniques to match the views. In order to compareimages in the wide-angle image domain, the digital video output of theslave PTZ camera may go through a reverse transformation in the imageprocessing circuitry 103 into a distorted slave image similar to that ofa portion of the raw wide-angle image of the master camera. The reversetransformation can take a rectangular image from the slave camera andcan transform it into a more complex shape with curved sides in thespace of the distorted wide-angle image.

In one example embodiment, the reverse transformation can be consideredto take place in two stages in the image processing circuitry 103. Givenknowledge of the pan, tilt and zoom of the slave camera, the first stagetransforms (x,y) coordinates in the slave image into world coordinates(θ,φ). This is the inverse of the transformation used to generatecorrected images within the master camera. If position feedback from thezoom level is unavailable, it can be ensured that the transition betweenmaster and slave views is always performed at the same zoom. Once worldcoordinates have been calculated, the second stage involves a projectionfrom world coordinates to the distorted image using a look-up table.This two-stage projection may be applied to individual pixels, totriangles that tessellate the slave image, or any other shape that tilesthe slave image.

In one example embodiment, the required PTZ control adjustments tocorrect the slave camera's view can be determined by comparing the colorand wavelet histograms of the two views. The corresponding imagetranslation vector can be transformed into the perspective-correcteddomain and used to generate the PTZ adjustment commands. Using only aproportion of this translation vector can maximize the convergence ofthe slave camera to the desired status. These PTZ adjustment controlsignals can be transmitted to the slave camera to obtain a better matchbetween the view from the slave camera and the perspective correctedview for the said RoI from the master camera. The image matching and PTZcontrol-sending process can be implemented in an iterative manner toachieve the desired matching accuracy, which can be determined by usingmean square error, mean absolute difference and histogram comparison, orother means.

The master and the slave cameras may have different color settings inpractice. Before performing registration, their color histograms can beequalized so that they both have the same dynamic range, brightness andexposure levels, and possible color offsets are also removed byhistogram equalization, which is a widely used image processingtechnique (see e.g., the text book entitled, Fundamentals of DigitalImage Processing by Anil Jain, Prentice-Hall, NJ, 1988, which is herebyincorporated by reference).

The master camera can have the functionality to support privacy regionswhich obscure user defined regions from being outputted, as described inthe U.S. patent application Ser. No. 11/178,232 entitled “ImageProcessing of Regions in a Wide Angle Video Camera,” which is herebyincorporated by reference. As the view from the slave PTZ camera and aperspective corrected RoI in the master camera are matched, masksrepresenting the shape of the privacy regions defined in the mastercamera can be applied to blank the appropriate regions in the slaveimage. In one example embodiment, this is done in the image processingcircuitry 103.

In one class of preferred embodiments, once the two images are matchedor registered, the control circuitry 104 dictates the desired image thatwill be composited in the image processing circuitry 103. If greatermagnification is required, the relevant perspective corrected view canbe replaced by the appropriately matched slave view. The intention of anexample of this embodiment is to transition between the master view andthe slave view as seamlessly as possible to create the quality of acontinuous zoom function. Outputs from the image processing circuitrycan include a number of perspective corrected views from the wide-angleimage, the slave camera's view, or a collage of multiple views includingany number of these.

The digital output is preferably passed to be formatted and compressedas necessary in the output circuitry 105 before being digitally outputto the base station for monitoring. For example, multiple MPEG4 streamsare possible. This process, describing the embodiment of FIG. 1, isillustrated using a flow chart in FIG. 8. The distorted wide-angle videoimage is captured using wide-angle master camera (Step 802). An RoI inthe master camera is then defined (Step 804). The estimated PTZ commandsare then transmitted to the salve camera from the master camera toachieve approximate view matching with RoI (Step 806). The output of theslave camera is then reverse transformed by the master camera (Step808). The distorted slave image is then compared with the distortedwide-angle image to determine and transmit adjustment PTZ controlsignals to the slave camera (Step 810) to determine whether the desiredmatching accuracy ahs been met (Step 812). If the desired matchingaccuracy has been met, then the process continues on to Step 814. If thedesired matching accuracy has not been met, then the process is loopedback to Step 806. Once the desired matching accuracy has been met, theperspective corrected master camera view is replaced by adjusted slavecamera view to achieve an expanded zoom function (Step 814).

The method and systems can have several slave cameras. Such method andsystems can track several moving regions at the same time by assigningeach moving object into a different slave camera producing a sharperimage of the moving blob. In this case, the perspective corrected viewof the master camera can be replaced by the adjusted views of the slavecameras tracking moving blobs. An example embodiment is shown in FIG. 1Bwhere a master camera controls two slave cameras with optional zoomcapabilities.

Another variation embodiment of these inventions can use analog videofor the output from the master camera. Conversion from digital-to-analogvideo and formatting can take place in the output circuitry 105. Anotherpossible embodiment consists of two analog composite video outputchannels.

Another embodiment can use an analog slave camera. The analog videoproduced by this camera can be converted into digital video using ananalog-to-digital converter (ADC) (206) as shown in FIG. 2. The outputcircuitry 205 can perform the formatting and compression required fordigital video output from the master camera. As mentioned for FIG. 1,variations of the embodiment in FIG. 2 include systems with analog videooutput from the master camera. Conversion from digital-to-analog videoand formatting can take place in the output circuitry 205.

Another embodiment with an analog-switching version of the system isshown in FIG. 3. In this embodiment the video from the slave PTZ camerais analog. The optical system 301, in conjunction with the image sensor302, can be used to capture an image that can then be passed to theimage processing circuitry 303 for correction. As mentioned in anexample embodiment above, the correction can be an image warp thatcompensates for distortions introduced by the lens. The image processingcircuitry 303, which can have a memory, can be comprised of either oneor a cascaded set of microprocessors coupled with a high bandwidth busto increase the available processing capability. The digital sensor datacan be sent to the image processing circuitry 303 through a buffer ordirectly if the circuitry operates at a sufficiently high speed. Thiscircuitry can also be responsible for debayering, color equalization andcolor balancing of the image. Characteristics of the image sensing 302,such as the exposure and aperture, and the image processing 303 can becontrolled by the control circuitry 304.

In one preferred embodiment, the decision for whether the view from theslave is necessary is dictated by the control circuitry resident in themaster camera 304, which can act on a resident software program and/orfrom base station control. The control from the base station can be anystandard, including RS485 or TCP/IP format. The slave camera,preferable, is not controlled directly from the base station, but viathe control circuitry in the master camera 304. It may be desirable forthe user to be unaware that multiple cameras are in use.

In one example embodiment, the control circuitry 304 can performapproximate view matching between the master, wide-angle video cameraand the slave PTZ camera if required. PTZ controls can be transmitted tothe slave camera from the control circuitry in the master camera toachieve an approximate matching. In one preferred embodiment, thisapproximation uses PTZ presets in the slave camera. An alternativeembodiment uses a slave camera, which can be commanded to turn to anyPTZ state. Another alternative embodiment uses a slave camera in whichthe camera's position output is predictable and consistent when PTZcommands are issued. In an example of this embodiment, the slave cameracould have a base that is controlled using stepper motors that areoccasionally calibrated to a known position. Another embodiment canutilize a calibration technique in which the user calibrates a finitenumber of positions so that both of the cameras are viewing the samecalibration object. The slave camera can then give a positional feedbacksignal, the value of which can be stored alongside the master cameraview's virtual PTZ coordinates in a table in memory. Linearinterpolation can be used to determine intermediate positions betweenthese calibrated points. The slave PTZ camera view can thus be sent to aposition in approximate matching with the desired RoI. In these analogsolutions, it is possible for the slave camera to be commanded to movebefore a threshold-zoom level is exceeded. This pre-emption can reducedelays due to the transit time of the mechanical slave PTZ camera.

The output from the image processing circuitry 303 can be passed to theanalog conversion and formatting circuitry 305 which can produce ananalog output from the digital data. The outputs from the analogconversion and formatting circuitry 305 and the slave PTZ camera can bepassed to video switching and output circuitry 306. This circuitry canbe controlled by the control circuitry 304, which decides which videostream should be output on the appropriate output channel. The outputfrom the video switching circuitry can be one or more analog videochannels.

The master camera can have the functionality to support privacy regionswhich obscure user defined regions from being outputted, as described inthe U.S. patent application Ser. No. 11/178,232 entitled “ImageProcessing of Regions in a Wide Angle Video Camera.” A mask representingthe shape of the privacy regions defined in the master camera can begenerated in the image processing circuitry 303. As the view from theslave PTZ camera and a perspective corrected RoI in the master cameraare approximately matched, this mask can be applied to blank theappropriate approximate regions in the slave image using the videoswitching and output circuitry 306. An alternative embodiment uses aslave camera having its own privacy region support that can becalibrated through the master camera.

FIG. 4 is a modified version of the embodiment in FIG. 3. In thisexample embodiment, the video from the slave PTZ camera is digitalinstead of analog. Thus the decision of which outputs to show can beconducted in the digital domain by the ‘multiplexing, compression &formatting circuitry’ 405. This can include an option of outputtingeither a single video stream or a combination of streams usingmultiplexing. The camera system can have a digital output (e.g. MPEG4).The mask representing any privacy regions defined in the master cameracan be applied in this circuitry 405 to blank the appropriateapproximate regions in the slave image. Apart from this final stage, therest of the process follows the same steps as the procedure describedfor FIG. 3.

An alternative embodiment is shown in FIG. 5 where the slave camera hasan analog video output that can be converted into digital video using ananalog-to-digital converter (ADC) 506. Otherwise it follows the sameprocess and layout as described in the description for FIG. 4.

The embodiment in FIG. 6 illustrates a layout in which video switchingmight not take place. The video output from the slave PTZ camera doesnot have to be passed to any circuitry in the master camera. The controlcircuitry 604 in the master camera can still be responsible for movingthe slave camera to the desired approximate location to view theselected RoI. The two cameras can have separate video outputs. Theoutput from the slave PTZ camera can be either analog or digital video.The digital output from the image processing circuitry 603 in the mastercamera can be formatted and compressed as necessary in the outputcircuitry 605 before being digitally outputted to the base station formonitoring. Multiple MPEG4 outputs are possible. A variation from thisembodiment is a system with analog video output from the master camera.Conversion from digital-to-analog and formatting of the digital datafrom the image processing circuitry 603 can take place in the outputcircuitry 605. A possible embodiment consists of two analog compositevideo channels. The output from the slave PTZ can be either analog ordigital video. Privacy regions can be implemented by using the slave PTZcamera's individual circuitry and configuration settings.

Motion Detection in the Master Camera:

Motion detection in the master camera can be carried out in preferredembodiments by using the well-known background-subtraction method. Thereare many public domain documents describing background estimation invideo. The background of the scene can be estimated in many ways. Thebackground image of the scene can be defined as those pixels belongingto stationary objects in the scene. For example, in the public domainarticle by R. Collins et al entitled “A System for Video Surveillanceand Monitoring,” which is hereby incorporated by reference, a recursivebackground estimation method is proposed based on the equation:

$\begin{matrix}{{B_{n + 1}\left( {k,l} \right)} = {{a\;{B_{n}\left( {k,l} \right)}} + {\left( {1 - a} \right)I_{n}}}} & {{{if}\mspace{14mu}{I_{n}\left( {k,l} \right)}\mspace{11mu}{is}\mspace{11mu} a\mspace{14mu}{stationary}\mspace{14mu}{pixel}},} \\{\mspace{101mu}{{= {a\;{B_{n}\left( {k,l} \right)}}},}} & {{if}\mspace{14mu}{I_{n}\left( {k,l} \right)}\mspace{11mu}{is}\mspace{11mu} a\mspace{14mu}{moving}\mspace{14mu}{{pixel}.}}\end{matrix}$where I_(n) (k,l) represent a pixel in the n-th image frame I_(n) of thevideo captured by the master camera, and the image B_(n+1) is theestimated background image at time instant n+1, and a is a parameterbetween 0 and 1. This recursive equation provides a weighted sum of pastimage frames. Temporary objects disappear over long time averaging andstationary objects of the scene remain in the background. The backgroundestimation process can be carried out by other means as well. Likewise,motion detection itself can be carried out by other methods, within thescope of the present innovations.

The moving pixels of the current image are preferably estimated bysubtracting the current image I_(n) from the current background imageB_(n). These pixels are then connected to a moving blob by connectedcomponent analysis, which is a well-known image processing technique(see e.g., Fundamentals of Digital Image Processing by Anil Jain,Prentice-Hall, NJ, 1988). Moving blobs in a video corresponds to personsor moving objects and they together with their local neighborhoods inthe video define Regions of Interest because persons, moving objects,left objects in the scene etc. are important in security monitoringapplications. Unlike conventional systems, which only capture recordedvideo for later analysis, real-time surveillance offers the addedbenefits of alarm and event triggers without delay. Therefore, suchregions should be tracked and zoomed for closer inspection.

Tracking in the Master Camera:

Once a moving blob is detected, it can be tracked by the master camera.One preferred embodiment carries out the tracking in the master cameraaccording to U.S. patent application Ser. No. 10/924,279, entitled“Tracking Moving Objects in Video Using Wavelet Domain Information” byA. E. Cetin and Y. Ahiska in the master camera using the wide-angleimage frames of the video. In this patent application moving blobs arecharacterized by a one-dimensional histogram constructed from color andwavelet domain information of the blob. Blobs in the current image frameof the video and blobs in the previous image frame are compared to eachother using the histograms of blobs. Histogram comparison is carried outusing the mean-absolute difference or the Bhattacharya coefficient.Blobs producing the smallest mean-absolute difference are associatedwith each other.

In another embodiment, tracking can be initiated by pointing on anobject. If the clicked pixel is inside a moving blob then this blob istracked as above in the plurality of image frames forming the video. Ifthe clicked pixel is not a part of a moving blob then a region-growingalgorithm is initiated around the clicked pixel and pixels havingsimilar characteristics are combined to form a blob. The color andwavelet histogram of the estimated region is compared with the histogramof the same region in the next image frame. If the color and wavelethistogram of this region changes over time then this means that theobject started moving. This also means that some portions the region arelikely to be a part of a moving blob determined by the motion detectionalgorithm of the camera. Once a decision is made that this stationaryobject is now a part of a moving object, then it is tracked as describedin the above paragraph.

In many surveillance applications it is very important to get a highquality picture of a person or a moving object. The tracking algorithmprovides the necessary information to get a closer picture of the movingobject. The wide-angle camera described in U.S. patent application Ser.No. 10/837,325, entitled “Multiple View Processing in Wide-Angle VideoCamera,” has a zooming capability. This capability can be expanded byusing a slave PTZ camera taking instructions from the master camera. AnRoI encapsulating the center of mass of the tracked blob can be used topass PTZ controls to the slave PTZ camera resulting in the salve camerazooming into the blob to achieve an expanded zoom capability.

The slave PTZ camera will often produce a sharper image of the blobcompared to the corrected view of the blob obtained from the masterwide-angle camera. This is because the master wide-angle camera zoomsinto a region by performing numerical interpolation, which smoothes theedges of the objects due to limited sensor resolution, in many casesleading to smooth pictures. By replacing the smooth picture obtainedfrom the master camera with the sharp picture from the slave camera, thezooming capability of the system is expanded. As persons and movingobjects (or objects which have moved in the past) are important insecurity monitoring applications, object tracking is useful in definingRoI for zooming to obtain a closer inspection.

As discussed earlier, a preferred embodiment can consist of a mastercamera and two slave cameras with optical zoom capabilities as shown inFIG. 1B. Alternative embodiments of the method and camera systems shownin FIGS. 2, 3, 4, and 5 can also consist of a single master and multipleslaves with optical zoom capabilities.

In one class of example embodiments, the method and systems have theflexibility of realizing the moving object tracking in the master cameraor in slave cameras provided that slave cameras have built-in trackingcapabilities. In one example of these embodiments, the master cameradetects moving regions in the scene and assigns each moving region to adifferent slave camera. Each slave camera can then track a moving regionusing built-in tracking mechanisms.

Image Registration in the Master Camera:

The image of the moving blob and its immediate neighborhood captured bythe slave PTZ camera and the corresponding view of the blob in themaster camera can be registered in the master camera to achieve ahigh-quality picture of the RoI. Image registration can be implementedin the master camera in two stages. In the first stage some salientpoints in both a portion of the image of the master camera containingthe moving blob and the transformed image of the PTZ camera can bedetermined by running the same algorithm in the two images. For example,if the master camera has an image from a fisheye, then the image of theslave PTZ camera is transformed into the distorted fisheye imagecoordinates. This also applies for other means of capturing wide-anglevideo such as using a peripheral lens. Since both images represent thesame blob in the scene, the salient point detection algorithm shouldproduce the same pixels as points of interest. Salient points can bedetermined using a wavelet domain method. After this stage the salientpoints of the two images can be matched to each other using the localcolor histograms around each point.

A flow chart describing an example embodiment of this image registrationalgorithm implementation for the master camera is illustrated in FIG. 7.The current image I_(n) represents the raw wide-angle image of themaster camera and the image J_(n) represents the transformed image ofthe slave camera. Using the I_(n) input, salient points in the image aredetermined (Step 702). Using the J_(n) input, salient points in theimage are determined (Step 704). These two salient points are matchedusing local histogram comparison (Step 706). This information is thenused to update the pixels of the image I_(n) of master camera using thepixels of J_(n) of slave camera (Step 708).

There are many public domain salient point detection algorithms in theliterature (see e.g., the text book entitled, Fundamentals of DigitalImage Processing by Anil Jain, Prentice-Hall, NJ, 1988). Commonly usedones include the Harris Corner detector and wavelet domain salientcorner detectors. Wavelet transforms in two dimensions carry both spaceand scale (frequency) information. A salient point of an image can bedefined as a pixel whose wavelet coefficients have relatively highamplitude values compared to other wavelet coefficients in all or someof high-frequency subband images of the wavelet transform. If a pixel ispart of a flat region in the image, then its corresponding waveletcoefficients are ideally zero or very close to zero. If a pixel is onthe horizontal (vertical) edge of an object then it produceshigh-amplitude wavelet coefficients in low-high (high-low) subband imageand another set of high amplitude coefficients the high-high subbandimage obtained after one stage of the wavelet transform. On the otherhand, if the pixel is on the corner of an object then it produceshigh-amplitude wavelet coefficients in low-high, high-low and thehigh-high subband images. Therefore significant corners of an image canbe determined by thresholding high-amplitude wavelet coefficients in allsubband images. It turns out that some of the salient points are on thecorners and significant edges of the moving blob and its immediateneighborhood in the background part of the image.

Once the salient points of both images are detected they have to bematched to each other to register the two images coming from the masterand slave cameras viewing the same object. The simplest matching processcan be carried out by comparing the values of the corresponding pixels.However this may lead to incorrect results because an object may consistof a single color and all salient points may have the same or similarpixel values. Therefore it is better to compare the local neighborhoodsaround the salient points to achieve robust results. In someembodiments, this matching is performed by comparing the local colorhistograms around the salient points. A color histogram around a pixelcan be determined in any color representation space. The most widelyused color representation schemes include Red, Green, and Blue (RGB) andluminance and chrominance representations (YUV or YCrCb).

The normalized color histogram of a local region O around a salientpoint p in the image I_(n) of the master camera is expressed as

${h_{p}(k)} = {\left( {1/N} \right){\sum\limits_{S\;{ɛO}}{\delta\left( {{q(s)} - k} \right)}}}$where s represents the color valued pixel s, O represents a local regionaround the salient pixel p, δ is the Kronecker-delta function, N is thenumber of data points in O, q is a quantizer function mapping the colorspace domain data into a L bit number. L is selected as 12 in thisembodiment. The color histogram h_(p), which is constructed from thecolor information around the pixel p characterizes this pixel.

Let h_(q)(k) is another normalized histogram around the salient pixel qin the image J_(n) of the slave camera. Histograms h_(p)(k) and h_(q)(k)can be compared to each other in many ways. Mean-absolute difference(MAD) gives a measure of comparison:

${{h_{p} - h_{q}}}_{1} = {\left( {1/K} \right){\sum\limits_{k = 0}^{K - 1}{{{h_{p}(k)} - {h_{q}(k)}}}}}$where K=2¹² is the number of points in the normalized color histogram.If the mean-absolute difference distance between p-th salient point andthe q-th salient point are smaller than distance between the othersalient points then p-th salient point of the image I_(n) is assigned tothe q-th salient point of the image J_(n).

Other color histogram comparison measures include the mean square error,cross correlation, and the Bhattacharya measure:

${D\left( {h_{p},h_{q}} \right)} = {\sum\limits_{k}\sqrt{{h_{p}(k)}{h_{q}(k)}}}$Higher the Bhattacharya measure D of h_(p)(k) and h_(q)(k) better thematch between the histograms h_(p)(k) and h_(q)(k).

Once the salient points of images from the master and the slave camerasare matched the pixels of the image I_(n) are updated in the mastercamera using the pixels of J_(n) according to the matched salientpoints.

Image registration in the system is preferably an iterative process. Atypical commercial PTZ camera can take finitely many (e.g. 128) possiblephysical viewing positions. The initial position information provided bytracking algorithm may not be accurate and as a result the PTZ cameramay cover only a part of the region of interest and/or tracked object.In such a case, some of the salient points determined on the image ofthe master camera may not be matched. This means that additionalposition information should be transmitted to the PTZ camera to matchalmost all of the salient points in both images. Also, the initiallyregistered image may not be detailed enough. For example, the trackedblob may be only a small portion of the image returned by the slave PTZcamera. The slave camera should zoom into the scene so that the trackedblob should become a large portion of the image returned by the slavePTZ camera. In this case, additional commands can be transmitted to theslave camera in an iterative manner as well. The iterative process canbe terminated after comparing the two images. The comparison ofdistorted slave image from the PTZ camera with the raw wide-angle videoimage can be performed using many commonly used image comparisonmeasures including mean square error (MSE), mean absolute difference(MAD), and matching the colour histograms the two images. If the MSE,MAD or color histogram difference between the two images drops below athreshold then the iterative registration process is terminated.

In the above paragraphs, the image registration process is described fora single slave camera. Extension of the above image registration methodto multiple slave cameras monitoring different RoI's is straightforward.Video images produced by slave cameras are placed on the perspectivecorrected view of the master camera one by one.

Slave cameras can communicate with the master camera via RS485 bus orany other bus capable of carrying positional data information.

Further Information

The following documents can be used for further information in the fieldof the invention and are hereby incorporated by reference.

References Cited:

-   U.S. Pat. No. 6,509,926, entitled “Surveillance Apparatus for Camera    Surveillance System,” which is hereby incorporated by reference.-   U.S. Pat. No. 6,724,421, entitled “Video Surveillance System With    Pilot and Slave Cameras,” which is hereby incorporated by reference.-   U.S. Pat. No. 6,147,709, entitled “Method and Apparatus for    Inserting a High Resolution Image Into a Low Resolution Interactive    Image to Produce a Realistic Immersive Experience,” which is hereby    incorporated by reference.-   U.S. patent application Ser. No. 10/837,326, filed Apr. 30, 2004,    entitled “Multiple Object Processing in Wide-Angle Video Camera,”    which is hereby incorporated by reference.-   U.S. patent application Ser. No. 10/837,325, filed Apr. 30, 2004,    entitled “Multiple View Processing in Wide-Angle Video Camera,”    which is hereby incorporated by reference.-   U.S. patent application Ser. No. 10/837,019, filed Apr. 30, 2004,    entitled “Method of Simultaneously Displaying Multiple Views for    Video Surveillance,” which is hereby incorporated by reference.-   U.S. patent application Ser. No. 10/924,279, filed Aug. 23, 2004,    entitled “Tracking Moving Objects in Video Using Wavelet Domain    Information,” by A. E. Cetin and Y. Ahiska, which is hereby    incorporated by reference.-   U.S. patent application Ser. No. 10/837,012, filed Apr. 30, 2004,    entitled “Correction of Optical Distortion by Image Processing,”    which is hereby incorporated by reference.-   U.S. patent application Ser. No. 11/178,232, filed Jul. 8, 2005,    entitled “Image Processing of Regions in a Wide Angle Video Camera,”    which is hereby incorporated by reference.    Public Domain Documents:-   [1]—X. Zhou, R. Collins, T. Kanade, and P. Metes, “A Master-Slave    System to Acquire Biometric Imagery of Humans at Distance,” ACM    International Workshop on Video Surveillance, November, 2003, which    is hereby incorporated by reference.-   [2]—R. Collins, Lipton and Kanade, “A System for Video Surveillance    and Monitoring,” in Proc. American Nuclear Society (ANS) Eighth    International Topical Meeting on Robotics and Remote Systems,    Pittsburgh, Pa., Apr. 25-29, 1999, which is hereby incorporated by    reference.-   [3]—“Fundamentals of Digital Image Processing” by Anil Jain,    Prentice-Hall, NJ, 1988, which is hereby incorporated by reference.    Modifications and Variations

As will be recognized by those skilled in the art, the innovativeconcepts described in the present application can be modified and variedover a tremendous range of applications, and accordingly the scope ofpatented subject matter is not limited by any specific exemplaryteachings given.

For example, it is contemplated that the present innovations can beimplemented using any number of different structural implementations. Analternative embodiment of the present invention includes, but is notlimited to, a single physical structure housing both master and slavecameras and all necessary circuitry, separate housings for the mastercamera, all slave cameras, and all necessary circuitry or anycombination of the above housing distributions.

In another class of contemplated embodiments, the present innovationscan be implemented by adding a fourth axis of mobility to the slavecamera. For example, the slave camera can Rotate as well as Pan, Tiltand Zoom.

Further, these innovative concepts are not intended to be limited to thespecific examples and implementations disclosed herein, but are intendedto included all equivalent implementations, such as, but not limited to,using different types of cameras for the master and slave cameras. Thisincludes, for example, using PTZ controllable for both the master andslave cameras. This also includes, for example, using cameras with zoomcapabilities for both the master and slave cameras, or for neither themaster nor slave cameras.

In another class of contemplated embodiments, the present innovationscan be implemented using, in addition to motion detection and objecttracking, 3d-perspective view comparisons to identify the RoI. Forexample, if the master camera was aimed at a row of windows, the imageprocessing circuitry could be programmed to ignore unimportant movement,such as leaves falling, and only identify as RoI open windows.

An alternative and less preferred embodiment of the present innovationscan be implemented using optical, digital, mechanical, or any of anumber of different ways of doing optical zooming.

An alternative embodiment utilizes two master cameras. These can be, butdo not have to be, positioned facing in opposite directions. Thesecameras can be, but do not have to be, fish-eye cameras. The advantageof this embodiment is that a global perspective can be achieved throughthe use of master cameras that may not have 360-degree viewingcapability otherwise. This embodiment does not exclude the use of one,single master camera with a 360-degree field of view, such as a domecamera.

In another class of contemplated embodiments, one or several mastercameras can control multiple slave cameras. These master cameras cancontrol the slave cameras each independently, in a hierarchy, or in anyof a number of different ways. In one example of this class ofembodiments, one or several master cameras control one or severalintermediate cameras, which control one or several slave cameras. Anexample implementation of this embodiment is the “daisy chain” the slavecameras so the master camera assigns separate tracking tasks eitherdirectly or indirectly through other slave cameras. The advantages ofutilizing several slave cameras include, but are not limited to,obtaining different views of a single RoI, capturing several RoI, and/orfollowing RoI as they pass behind physical structures. In an example ofthis embodiment, the slave cameras

In another embodiment, the slave camera can have built-in trackingcapabilities. In this embodiment, the slave camera could take over thetracking job after the master camera had assigned it. The master cameracould then assign another tracking task to another slave camera.

In another class of contemplated embodiments, the master and/or slavecameras can be equipped with any of a number of different visionenhancements, including, but not limited to, night vision, infraredvision, or heat-sensing ability. The advantages of thermal sensitivityinclude, but are not limited to, better detection and tracking of heatproducing objects such as cars, people and/or animals. The advantages ofutilizing night vision or other low-light vision enhancement include theability to monitor an unlit area at night.

None of the descriptions in the present application should be read asimplying that any particular element, step, or function is an essentialelement, which must be included in the claim scope: THE SCOPE OFPATENTED SUBJECT MATTER IS DEFINED ONLY BY THE ALLOWED CLAIMS. Moreover,none of these claims are intended to invoke paragraph six of 35 U.S.C.§112 unless the exact words “means for” are followed by a participle.Moreover, the claims filed with this application are intended to be ascomprehensive as possible: EVERY novel and non-obvious disclosedinvention is intended to be covered, and NO subject matter is beingintentionally abandoned, disclaimed, or dedicated.

1. A method of automatically expanding the zoom capability of a wideangle video camera comprising the steps of: capturing a wide angle videoimage using a master camera which is capable of generating a transformedview image of all or part of said wide angle image; monitoring at leasta part of the area covered by said master camera from a steerable slavevideo camera which is in close proximity to said master camera;automatically controlling the field of vision of said slave camera fromsaid master camera, wherein at least some of the control signals to saidslave camera are fed from the master camera to achieve an approximatematch between said transformed view and estimated said slave cameraview; replacing said transformed view of said master camera by saidimage from said slave camera in master camera output to achieve expandedzoom capability for said master camera; and replacing at least one imageoutput portion from said master camera with a second image portion,which is registered to said one portion, to accordingly output a singleimage; wherein video output from said slave camera is fed to said mastercamera for reverse transformation into a similar projection as said wideangle image; and wherein said reverse transformed image is compared tosaid wide angle image for determining adjustments to said controlsignals for controlling said slave camera.
 2. The method of claim 1,wherein said method of reverse transformation and control signaladjustment is repeated in order to achieve a desired view matchingaccuracy.
 3. The method of claim 1, wherein said control signals to saidslave camera include an adjustment calculated at least in part from therelative positions of said master and slave camera or from feedback fromthe slave camera.
 4. The method of claim 1, further comprising usingmore than one slave camera within close proximity of said master camera.5. The method of claim 1, wherein said master and said slave camera orcameras share circuitry.
 6. The method of claim 1, wherein at least someof the control signals to said slave camera fed from the master cameraoriginate at a connected base station.